Prior U.S. patents of magnetic core winders, which include but are not limited to toroidal winders, include U.S. Pat. Nos. 5,331,729; 4,379,527; 4,872,618; 6,557,793; 4,288,041; and 5,875,988. In general, the prior art, as shown in FIGS. 1 through 3, illustrate the principle of winding magnet wire on a magnetic core (hereinafter “core”) to create an inductor. The prior art uses a supply ring 10 and winding ring 20 with pullout or open/close type ring openings 12 and 22 to enable a core 30 to be arranged with the rings 10 and 20 passing through the center hole of the core 30. In the prior art the openings 12 and 22 are opened manually and the core 30 is passed through the openings so that each ring passes through the center hole 32 of the core, with the central axis 34 of the magnetic core 30 at right-angles to the central axis 25 of the rings.
The supply ring 10 has a U-shaped groove 14 around its circumference. In order to enable wire 40 to be wound into the groove 14, the end of the wire 40 is manually attached to the supply ring 10. The winding ring 20 has substantially the same diameter as the supply ring 10, with which it is aligned concentrically. The winding ring 20 has a wire guide 24 via which wire 40 is drawn from the supply ring 10 and a guide roller 26 to guide the wire 40.
In an actual winding operation, the core 30 is first manually inserted onto the rings 10 and 20 via the openings 12 and 22 and positioned as shown in FIG. 2. The end of the wire 40 is then attached to the supply ring 10 and the supply ring 10 is rotated around its central axis to wind the required amount of wire 40 into the groove 14. After cutting the trailing end of the wire 40, the cut end is passed through the wire guide 24 and around the guide roller 26, and is drawn radially outwards from between the rings and affixed to a retainer means or the like (not shown) provided on the periphery of the core 30.
As shown by FIG. 3, when the core 30 is being wound, a drive (not shown) is used to rotate the supply ring 10 and winding ring 20 in the opposite direction from that used to load the wire 40 onto the supply ring 10, and the wire 40 is drawn from the supply ring 10 through the wire guide 24 and guide roller 26 on the winding ring 20 and attached to the core 30. In this state, the wire wound around the supply ring 10 is spirally wound a required number of turns around the core 30, and the wire left over on the supply ring 10 is manually removed. Finally, the core wound with the wire, that is, the inductor, is removed.
The ideal single layer inductor would have a low temperature rise, high inductance, and small size. Moreover, it has been found that by increasing the wire size, total number of turns, and decreasing the core size, these more desirable properties can be achieved. Moreover, since rectangular wire has a smaller width then round wire (for a given gauge), rectangular wire may be used to increase the number of turns on a core and thus increase the inductance. As such, U.S. patents directed to manufacturing or forming rectangular wire from round wire are found in the art, for example, U.S. Pat. No. 6,553,650.
The winding of rectangular wire on the edge however is extremely difficult. Referring now to FIG. 4, when the wire 40 forms around the corners 34 of the core 30, the wire has a tendency to twist and lie diagonally. If the wire 40 is guided tightly on either side of the corner, the twisting can be prevented but in winding a core there is insufficient space to guide the wire as it wraps around the internal wall 36 of the core 30. In some instances, the rectangular wire is formed and the core has a piece cut therefrom which permits the wire to be slipped onto the core. However, when a piece is removed the magnetic properties may decrease and the inductance of the core may be reduced.
It is thus an object of the present invention to overcome the problems associated with the prior art while maintaining an inductor with a low temperature rise, high inductance, and a small size.